Chlorinated rubber compound and process of making same



Patented June 30, 19 25.

UNITED STATES (PATENT OFFICE.

CARLETON ELLIS AN-D NORRIS ."BOEHMER, TO CHADELOID CHEMICAL COMPANY,

OF MONTCLAIR, NEW JERSEY, ASSIGNORS A CORPORATION OF WEST VIRGINIA.

No Drawing. Application filed May 18,

T0 (ZZZ whom it may concern:

Be it known that we, CARLEToN ELLIs and NORRIS BOEHMER, citizens of the United States, and residents of Montclair, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Chlorinated Rubber Compounds and Processes of Making Same, of which the following is a specification.

This invention relates to chlorinated rubber compounds and to the process of making same and relates especially to products obtained by treating rubber with chlorine in a liquid state or under high pressure, the chlorine preferably being used in excess to form perchlorinated compounds of novel properties. I

Ordinary raw or unvulcanized rubber is dilticultly soluble in various organic solvents and forms extremely viscous solutions which are slow-drying and form a sticky coating which is rather readily oxidized and disintegrated. Raw rubber therefore cannot be used advantageously for coating purposes. By chlorinating rubber the solubility is improved and the drying qualities greatly en hanced. These qualities in a general Way improve witlrthe degree of chlorination. Chlorine combines readily with rubber to form lower chlorinated compounds, 4 mols of chlorine being generally regarded necessary to form a saturated compound or rub ber tetrachloride. This addition compound contains approximately per centof chlorine. While its solubility in organic solvents is greater than that of the raw rubber it is not sufficient for many purposes. By treating rubber in carbon tetrachloride with chlorine at ordinary atmospheric pressure it is possible to increasethe. degree of chlorination by introducing chlorine by substitution, hydrochloric acid being evolved. In this way hexa or hepta chlor rubber may be obtained. These compounds however lack certain qualities which exist in chlorinated compounds of a higher stage of chlorination.

It isparticularly an object of the present invention to produce such compounds of a higher stage of chlorination or what may be termed perchlorinated rubber. Products of intensive chlorination of rubber which have a perchlorinated structure are relatively very soluble in various hydrocarbons and are notably resistant to reagents .For example films of such material which-have been ex- .of pressure.

1923. Serial No. 639,983.

posed to the action of concentrated nitric,

' other industries.

The raw material employed is crude or unvulcanized rubber such as ordinary crepe rubber. Rubber latex also may be treated by the present process. The presence of sulphur in the rubber generally speaking is undesirable especially when present in any extensive amount as the chlorine unites With the sulphur to form sulphur chloride which reacts upon the rubber to form insoluble bodies. Therefore when solubility is an important consideration vulcanized rubber should not be used. For some applications however vulcanized rubber such for example as old inner tubes of automobiles may be treated by the present process. Recovered rubber also may be used in some cases. The process also contemplates the treatment of gutta percha or balataor products of a nature kindred to rubber.

The chlorine used may be ordinarily liquid chlorine or chlorine under high pressure. In order to increase the pressure and rate of chlorination the receptacle containing the liquid chlorine may be heated if desired.

In carrying out the invention a preferred method is that of submerging masses or fragments of the rubber in liquid chlorine or running liquid chlorine onto fragments or sheets of rubber and permitting the reaction to progress in a confined space in order to secure the very desirable accelerating elfect By employing an excess of chlorine over that which the rubber would combine with chemically a solvent elfect is secured which gives rise'to products of novel qualities. The excess of chlorine acts as a solvent or flux and the resultant product may vary from a viscous mass to a thin liquid depending upon the quantity of chlorine which has been introduced. Liquid chlorine has a notable solvent action on chlorinated rubber and on exposure of the mass to atmospheric pressure or upon a reduction in pressure the excess of chlorine is removed to a greater. or less extent. When the chlorine has been largely expelled from a solution of perchlorinated rubber in liquid chlorine frequently masses of the perchlorinated product will be found which are clear and transparent possessing a light yellow color. The rubberoriginall used may be substantially opaque but the chlorinated product obtained from solution in 11q'u1d chlorine in some cases will be a clear transparent mass. This transparency is more particularly noticeable in the bubbles or. films which form in the container on evaporatin such a solution. In thicker masses especlally on account of the formation of many small bubbles and possibly too the presence of impurities as for example iron compounds from the walls of the vessel give the product a more opaque appearance.

The present invention therefore contemplates treating rubber with an excess of chlorine under high pressure preferably in the liquid state and preferably also at temperatures elevated slightly above ordinary room temperature to yield chlorinated or perchlorinated rubber products which have .passed through a flu'xmg stage due to the solvent action of an excess of chlorine which therefore have been ex osed to the action of bhlorine under conditions highly favorable for intensive chlorination and the production of rubber compounds containing chlorine present in an amount rangin upwards to well over 70 per cent of com ined chlorine. Thus octo, nono, deca and even higher stages of chlorinated rubber may be obtained. The product derived by the concurrent chlorinatingand fluxing action of an excess of chlorine on rubberconstitutes a feature of the present invention. The use of more chlorine, in the initial stage of the process, than can combine with therubber, is hereinafter referred to in the expression. in excess of combining requirements.

The chlorine is preferably fairly pure .although works chlorine which normally.

chlorine under pressure.

contains some oxygen or air and other impurities may be used in some cases. Also it is possible to introduce into the chlorine various other reactive or catalytic substances such as bromine or iodine.

. Procedures which will serve to illustrate the present invention, but which are capable of various modifications as will now be apparent from this disclosure are the follow- %'aaam'ple 1.202 grams of crepe rubber in the form of a loosely wound spiral was placed inan open lead vessel to prevent contact with iron, which in turn was placed inside of an apparatus designed to contain This apparatus was-connected to a cylinder of liquid chlorinein such a way that only the as therefrom could pass over into thechlormating vessel.

The chlorination was made at ordinary atmospheric temperatures rangmg from 11 to 29 (3., the average being in the neighborbeing vented-from the chlorinating vessel every 24 hours in order to purge it from hydrogen chloride which is alsoformed dur-- ing the reaction. The product formed in;

this experiment was in the form of a con-' solidated mass of material of yellow or greenish yellow color and vesiculated structure. It weighed 707 grams and after washing in order to remove uncombined chlorine, hydrogen chloride and other impurities, it was ground and found to be soluble in benzol and similar hydrocarbons.

The use of chlorine under higher pressures accelerates the reaction as shown in the following example. l

Example 23-193 grams of crepe rubber were placed in a chlorinating vessel similar to that described inExample 1 and subjected to chlorine under high pressure. The liquid chlorine cylinder as well as the chlorinating vessel were heated slightly above the atmospheric temperature by means of warm water in order to increase the pres: sure of the chlorine. In this case the chlorine pressure varied from 240 to 320 pounds per square inch as shown on the gauge connected with the a paratus averaging in the neighborhood of 220 pounds per square inch. The temperature measured on the inside of the chlorinating vessel ranged from 57 to 67 C. Chlorination in this instance was continued for 12 hours after which on inspection it was found that the reaction was not complete. Chlorination was therefore continued for 17 hours longer under the same conditions making a total of 29 hours chlorination. The product in this case was a consolidated vesiculated mass similar in all respects to that described in Example 1.

Liquid chlorine in contact with the rubber to be chlorinated tends to enhance the uniformity of'the reaction and still higher pressures make the reaction still more rapid as; shown in the following procedure.

Example 3.- 127 -.gramsofv crepe rubber were placed in the chlorinator described in Example 1 and this was connected to the liquid chlorine cylinder. The cylinder was then heated; somewhat above atmospheric temperature by means of warm water while the chlorinator was kept cool by means of distilled over from the cylinder and condensed again as a liquid in the chlorinator thus bringing the rubber in direct contact with liquid chlorine. After the requisite amount had distilled the chlorinator was shut off from the cylinder by means of a valve and heated until the temperature shown on the inside of the vessel was 60 to C. averaging 70 C. The corresponding pressure being 323 pounds per square inch. After 27 hours chlorination under these conditions the chlorinator was vented rapidly and the vessel opened. The lead inner vessel was found to contain a dark green viscous fluid consisting of a solution of the chlorinated product in chlorine. Up'on standing open to the atmosphere the greater part of the chlorine evaporated yieldinga consolidated vesiculated product similar to those described in Examples 1 and 2. Upon breaking this mass apart it was found that small pieces of the mass were translucent or transparent and of a rather good lustre. The whole mass however, on account of the bubbles occurring in the vesiculated structure, appeared opaque.

If desired the rubber may be cut or shredded into small pieces before chlorination in order to improve the uniformity and rapidity of penetration of the chlorine.

Also the material may be partly chlorinated until it is sutiiciently brittle to be broken up and ground and this ground material may then be again subjected to the action of chlorine until the reaction .is complete and a highly soluble substance is formed.

This also has the advantage of improving the accessibility to the chlorine of the material to be reacted upon.

The material obtained in all of the above examples after washing became white or very light yellow in color and could be ground readily to a coarse powder.

From the foregoing it will be noted that liquid chlorine causes rubber to swell and if enough is present a more or less homogeneous solution maybe formed. Some observations tend to show that partially chlorinated rubber will form a more mobile solution than the raw rubber. This is in line with the general solubility characteristics of these substances. 1

However, it is found that gaseous chlorine under high pressure is taken up by the rubber in much the same way, but, it is probable, to a less extent. Both methods yield a consolidated mass of chlorinated rubber of a somewhat more compact and completely unified character than that described in copending applicationsas coalesced. The employment of gaseous chlorine under high pressure renders useful the employment of temperatures somewhat above ordinary room temperature, 7 0-7 5 C. being satisfactory. Temperatures as low as 2025 C. with corof fair sized bubbles.

respondingly lower pressures may be employed but a longer time is necessary for the reaction.

Below certain minimum pressures the softening or solution of the rubber does not 5- appear to take place. At temperatures of 20 C. and lower this minimum pressure is chlorine be present, a solution of chlorinated rubber will be formed.

When the greater part of the uncombined chlorine is allowed to evaporate spontaneously without elevation of the temperature, the resulting mass is composed of clear, lustrous material, enclosing a large number Thin films may be formed, which are transparent and very similar to films formed from the more usual solvents such as benzol.

High pressure chlorine, either with or without the actual presence of the liquid phase makes possible the formation of very highly chlorinated products, containing, if

desired, 70 percent or more of combined chlorine. Preferably products containing at least 50 percent of combined chlorine are derived by the present process.

A sample of chlorinated rubber made by treating rubber with liquid chlorine was found in one case to contain between 68 The film will burn when placed in a flame but does not readily support combustion.

Placed on a laboratory hot plate the film swelled to a white mass contalning bubbles.

It may be noted that water present in the rubber or inthe chlorine gas will collect at the bottom of the chlorinating chamber forming a strongly acid solution. When the separation of water occurs in any large measure provision should be made for its withdrawal ora false bottom provided which will allow aspace in which the water At about 170 C. the fragments of .the chlorinated rubber began to adhere.

may collect. The submergence of a portion of the rubber in acidulated water is not favorable for most uniform chlorination. When a product of lower quality is to be made the precaution of withdrawing the separated water generally is unnecessary.

One Way of expressing the preferred procedure of the present invention is that of chlorinati-ng rub-ber by exposing it to compressed chlorine in plasticising proportions to cause softening of the material undergoing chlorination, using chlorine either in gaseous or liquid form and on completion of chlorination to the degree desired in removing the excess of chlorine which is present to confer plasticity. The degree of plasticising may be slight or it may progress to various stages until a solution of the chlorinated rubber results.

This case is in part a continuation of Serial No. 57 5,045, filed July 15, 1922.

What we claim is L- 1. A chlorine-fluxed chlorinated rubber.

2. A chlorine-fluxed chlorinated rubber containing in excess of two-thirds of its weight of combined chlorine.

3. The process which comprises exposing rubber to the action of compressed chlorine in an amount substantially in excess of combining requirements whereby a chlorinefiuxed chlorinated rubber-is obtained.

4. The process which comprises bringing chlorine under pressure into contact with fragments of rubber, the amount ofchlorine employed beingsubstantially in excess of the maximum combining requirements of the rubber and suificient to form ,a solution of chlorinated: rubber in chlorine.

5. The process of chlorinating rubber which consists in exposing the rubber to chlorine in such proportions under superatmospheric pressure as to produce a plastic mass to cause softening of the material undergoing chlorination and removing the excess of chlorine after chlorination has been carried to the desired stage.

6. As a new product, a plastic mass containing chlorinated rubber and 'a substantial amount of liquid free chlorin, such free chlorin serving as a plasticising agent fo the normally solid chlorinatedrubber. 7.v The process which comprises softening unvulcanized. rubber by exposing to more than double its weight. of chlorine, under 'a liquefyin'g temperature and pressure, where.

eagues by the rubber is softened, and permitting the chlorine to act upon the softened material to bring about substantial chlorination thereof. 8. The process which comprises softening unvulca'nized rubber by exposing to more than double its weight of chlorine, under a liquefying temperature and pressure, whereby the rubber is softened, andpermitting the chlorine to act upon the softened material to bring about substantial chlorination thereof, no solvent except chlorine being present.

9. The process which comprises softening unvulcanized rubber with several times its weight of chlorine in a liquid state and permitting reaction to take lace, whereby a highly chlorinated rubber is produced.

10. A process which comprises introducing free chlorin into contact with unvulcanized rubber under pressure, until a. softened mass is formed, and continuing the treatment un til the rubber has combined with substanchlorin.

unvulcamzed rubber, substantially. more thandouble its own weight of chlorin, under pressure and temperature conditions allowing the direct formation of a soft plastic mixture.

12. An intermediate product in the production of chlorinated rubber comprising a plastic mixture containing chlorinated rubber and liquid. chlorin.

13. The process which comprises exposing rubber softened by the action of liquid chlorine, to the action of chlorine under pressure, the latter being in an amount substantially in excess of combining require ments, and at an elevated temperature below the charring point ofthe material.

14. The process of making chlorinated rubber which comprises reacting with chlorlne under superatmospheric pressure and at a temperature which is initially considerably above ordinary room tem rature, but below the charring ,point of this material, on a loosely-packed mass com rising pieces of rubber softened by the action of liquid chlorine, the mass being freely permeable to 05 I chlorine, thus'bringing about an exothermic reaction and consolidating the pieces into a coherent mass of chlorinated rubber.

CARLETON ELLIS. roams BOEHMER.

rocess which comprises adding to 

